1. Field of the Invention
This invention relates to a novel container, and more particularly, to a container for housing an expandable food package in a stored, non-expanded condition and in an expanded condition having substantially increased volume, the container being constructed of non-metallic materials for use in a microwave oven.
2. Description of the Prior Art
Expandable food packages have been constructed for use, for example, in packaging and cooking corn kernels to form popcorn. Generally, the package is placed over a heat source under the influence of which cooking fats or oils, placed in the package, melt and form a gas while simultaneously the corn kernels are cooked to form the popcorn. The combination of expanding gas and puffing of the corn kernels cause the package to expand.
Prior art packages and containers for cooking such an expandable food generally utilize a shallow metal container for holding the food to be cooked by a thin aluminum foil cover. The cover expands under the influence of internal pressure from the cooked food to provide an internal volume greater than the original size, enabling the cooked food to be retained within the metallic container. An example of such a container or package is illustrated in U.S. Pat. No. 3,244,356 to Wolowicz, issued Apr. 5, 1966.
A principal advantage of using an expandable package in a container in which cooking can be performed, is the resulting economy of space in the storing and stacking of the packaged containers. Another advantage is the convenience for the user of not having to transfer or handle the cooking ingredients stored in the package. Unfortunately, packages incorporating metals, such as aluminum foil, cannot be used in a microwave oven because the metal acts as a shield, thereby preventing the energy from reaching the food to cook it. Therefore, in such packages, the food cannot be heated and cooked. As a result, it has become necessary to design a container for an expandable food package which is entirely non-metallic, so it can be used in a microwave oven heating environment.
One such package is illustrated in U.S. Pat. No. 4,036,423, issued to Gordon on July 19, 1977. In this patent, a non-metallic container for an expandable food package is formed from sheet material such as paperboard, polyethylene, paperboard lamination or combinations thereof sufficiently resistant to leakage of cooking oils and fats. The container includes a base portion and a cover. The base portion includes an open container section having a polygonally-shaped bottom panel having side panels connected thereto which taper upwardly and outwardly to receive food, such as uncooked kernels of corn with congealed cooking oil. An expandable cover is integrally attached to a flange portion connected to the side panels of the container along its entire outer periphery to enclose the base portion and food within the container. The flange and integral cover are then folded on top of the base and side panels to complete the construction. In use, the flanges are unfolded and the cover allowed to expand upon heating of the corn kernels and congealed cooking oil in a microwave oven; the cover expanding as the kernels expand. After cooking, the cover can be removed to expose the kernels for eating.
A principal disadvantage of the container illustrated in U.S. Pat. No. 4,036,423 is that the expandable cover is formed integrally with the container. This requires an additional manufacturing step during the formation of the container and requires the modification of standard carton closing machines in the manufacture of the finished container, both of which are highly undesirable, as they increase the cost of manufacture of the container.
Furthermore, the expanded food product has little room to expand laterally without causing rupture of the container side walls. Accordingly, the area of expansion of the product cannot be readily controlled within the perimeter or confines of the container, but must rely on the elasticity of the packaging material and/or integral cover on the container, which may prematurely rupture before cooking is complete, causing the expanded food product to be thrown from the container.
In accordance with the present invention, the expandable food package is completely separate from the container and is loaded into the container prior to closing the same.
The container of the present invention also features arcuate, concave side walls whereby the sides of the container can expand to confine the expanded food product within the perimeter of the container upon heating in a microwave oven.
Finally, the container is formed from paperboard or chemically treated, grease-resistant paperboard lamination whereby it is especially suited for use in a microwave oven.